Ore Deposit Geology

List of boxes page viii
Preface ix
Acknowledgements xi

1 What is an ore deposit? 1
1.1 Definition and scope of ore deposit geology 1
1.2 Ore deposit geology and related sciences 2
1.3 The geology of ore deposits 10
1.4 Ore deposit geology as a science: classifications and deposit models 14
1.5 The future of ore deposit geology 17
Questions and exercises 20
Further readings 21

2 Magmatic ore deposits 22
2.1 Petrological and geochemical background to magmatic ore formation 22
2.1.1 Processes of magma development 22
2.1.2 Partitioning of elements between phases – the common process of chemical evolution in magmatic systems 23
2.2 Types of magmatic ore deposits 24
2.2.1 Deposits formed from small-fraction partial melts: light rare-earth element (LREE) ores in carbonatites 27
2.2.2 Deposits formed during differentiation of a silicate melt: chromite deposits 32
2.2.3 Deposits formed from immiscible sulfide melt phases: base-metal Ni–Cu sulfide deposits in mafic and ultramafic rocks 42
2.2.4 Deposits formed from immiscible sulfide melt phases: PGE sulfide deposits 61
2.2.5 Deposits formed through extreme fractionation of magma: rare-metal pegmatites 76
2.2.6 Ores formed through incorporation of a mineral from depth in the Earth into magma: diamond deposits in kimberlites and lamproites 80
Questions and exercises 87
Further readings 90

3 Hydrothermal ore deposits I: magmatic and orogenic environments 92
3.1 Hydrothermal systems: generalities and background 93
3.1.1 What fluids form hydrothermal systems? 93
3.1.2 Components of a mineralising hydrothermal system 94
3.1.3 Mass-balance requirements for the formation of hydrothermal ore deposits 95
3.1.4 Hydrothermal solution chemistry, aqueous complexes and mineral solubility 95
3.1.5 Products of hydrothermal fluid flow 98
3.2 Hydrothermal deposits formed around magmatic centres 100
3.2.1 Porphyry deposits 105
3.2.2 Greisens and related ore deposits 132
3.2.3 Skarn and carbonate-replacement deposits 135
3.2.4 Polymetallic veins and vein fields associated with magmatic centres 148
3.2.5 High-sulfidation epithermal Au–Ag deposits 151
3.2.6 Low-sulfidation epithermal deposits 164
3.2.7 Volcanic-hosted massive sulfide (VHMS) deposits 183
3.3 Syn-orogenic hydrothermal ore deposits without close spatial or temporal relations to magmatism 199
3.3.1 Orogenic Au deposits 201
3.3.2 Carlin-type gold deposits 216
3.3.3 Iron oxide–copper–gold (IOCG) deposits 224
Questions and exercises 236
Further readings 238

4 Hydrothermal ore deposits II: sedimentary environments 241
4.1 Hydrothermal fluids in sedimentary basins 241
4.1.1 Chemical characteristics of basinal waters 242
4.1.2 Large-scale fluid flow in sedimentary basins 246
4.2 Base-metal deposits in sedimentary basins 248
4.2.1 Mississippi Valley-type (MVT) Pb–Zn deposits 249
4.2.2 SEDEX Pb–Zn–Ag deposits 261
4.2.3 Kupferschiefer or red-bed copper deposits 269
4.3 Uranium deposits in sedimentary basins 275
4.3.1 Unconformity-related uranium deposits 277
4.3.2 Tabular uranium deposits 280
4.3.3 Roll-front uranium deposits 284
Questions and exercises 287
Further readings 288

5 Ore deposits formed in sedimentary environments 290
5.1 Chemical precipitation from surface waters (hydrogene deposits) 290
5.1.1 Iron ores in ironstones 292
5.1.2 Sedimentary-rock-hosted Mn deposits 307
5.1.3 Sedimentary-rock-hosted phosphorus deposits 311
5.2 Ore deposits in clastic sedimentary environments 316
5.2.1 Heavy-mineral sand deposits on shorelines and palaeoshorelines 318
5.2.2 Fluvial placer and palaeoplacer deposits 322
Questions and exercises 334
Further readings 335

6 Supergene ores and supergene overprinting of ores 337
6.1 In situ supergene ores 339
6.1.1 Bauxite in lateritic weathering profiles 341
6.1.2 Ni–Co laterite deposits 346
6.2 Supergene ores formed by overprinting of hypogene ores 348
6.2.1 Supergene gold ores in lateritic weathering profiles 349
6.2.2 Supergene copper ores in arid and semi-arid climates 349
Questions and exercises 355
Further readings 355

Glossary 357
References 369
Index 392